Single-thrust bearing for a shock absorber

ABSTRACT

A single-thrust bearing for a shock absorber with a columnar journal projecting in the damping direction and which is sealingly surrounded by a flexible, annular-shaped membrane, whereby the membrane is secured in its rim area, which projects radially to the outside, to a supporting bearing and separates two liquid-filled working chambers from each other. The working chambers are defined in the area of the extremities which mutually oppose each other by hollow-conical bearing springs made of a rubber elastic material. The bearing springs are supported in their base area on the supporting bearing and are braced against one another by means of the journal by way of their tips which are turned away from each other.

This application is a division of application Ser. No. 08/213,364, filedon Mar. 14, 1994, now U.S. Pat. No. 5,474,284, which is a continuationof application Ser. No. 07/871,429, filed Apr. 21, 1992, now abandonedwhich is a continuation of application Ser. No. 07/780,147, filed Oct.21, 1991 now abandoned.

BACKGROUND OF THE INVENTION

The invention relates generally to single-thrust bearings for shockabsorbers, and more particularly to a single-thrust bearing with acolumnar journal projecting in the damping direction and which issealingly surrounded by a flexible, annular-shaped intermediary member.This intermediary member is secured in its rim area to a supportingbearing and separates two liquid-filled working chambers from eachother. The rim area of the intermediary member projects radially to theoutside. The liquid-filled working chambers are connected at least byone duct-type connecting port and are sealed to the outside by means offlexible terminating walls. These terminating walls are secured andsealed on one side to the journal and on the other side to thesupporting bearing.

Such a single-thrust bearing is known from the German Patent 38 02 105.The intermediary member mentioned therein is a bearing spring andseparates two working chambers from each other. These working chamberare sealed to the outside by means of membrane-type terminating walls.These types of single-thrust bearings have limited damping action andservice life.

The present invention is directed to the problem of developing asingle-thrust bearing with considerably improved damping action andservice life.

SUMMARY OF THE INVENTION

The present invention solves this problem by providing the intermediarymember with a membrane, by forming the terminating walls usinghollow-conical bearing springs, by inserting the bearing springs withtheir tips pointing away from each other, and by bracing the bearingsprings against one another by means of the journal.

This completely eliminates the contraction strains, which are caused bythe heat vulcanization of the rubber elastic material of which thebearing springs are made--resulting in an improved service life. Anadvantageous refinement occurs when the bracing, which actually is apressure pre-loading, is chosen so as to completely rule out theoccurrence of tensile stresses in the bearing springs, even duringabsorption of vibrations.

Due to the mutual bracing of the hollow-conical bearing springs, alatent overpressure prevails in the two working chambers of thesingle-thrust bearing according to the present invention. This preventsoccurrences of cavitation during the time that vibrations areintroduced, thus improving long-term durability.

A damping action results in the single-thrust bearing according to thepresent invention when large-amplitude vibrations are introduced. Thisdamping action is definitively based on the pressing of liquidcomponents through the connecting port. The damping action is effectivein a wide band, i.e. over a large frequency range, when the connectingport is designed as a choke opening. However, there are also applicationcases in which a high-quality damping action is desired for a specificfrequency range. For such applications, a duct-type shape is recommendedfor the connecting port, as well as dimensions that produce a resonantmovement of the bulk liquid surrounded by the connecting port, whenvibrations of the frequency to be damped are introduced.

Due to the existence of a connecting port between the two workingchambers, the pressure difference resulting in these chambers undernormal operating conditions is only relatively small. The intermediarymember between the working chambers can have a membrane-like thin shapeand consist of a rubber elastic material. In this case, one does nothave to fear premature destruction. The relative mobility of the journalin relation to the journal bearing is thus not significantly impeded.

The membrane can be flexibly expanded by the journal in the area of itsinner circumference, in order to simplify the required mutual sealing ofboth parts. Independently of this, it is of course possible to usesecondary sealing means.

It has proven to be particularly advantageous when the membrane contactsthe journal in a way that allows relative displacement. This enables anydestruction resulting from increased spring-deflection movements of thejournal to be effectively countered.

With respect to attaining a long service life, it has proven to beadvantageous when the membrane is provided in the area of its innercircumference with a bulge-like circumferential thickening. This enablesthe radial contact pressures which are transferrable to the journal tobe increased, so that an improved sealing action results. In addition,in variants capable of relative shifting, the wearing volume isenlarged, thus improving longevity.

Inside the supporting bearing, the membrane can have a U-shaped profilethat projects radially in the damping direction and surrounds thejournal coaxially. In such a design, the deformability corresponds tothat of a rolling diaphragm, so that the relative mobility of thejournal is improved in relation to the supporting bearing and isparticularly advantageous as far as the insulation of acousticallydisturbing vibrations is concerned. These types of vibrations can resultin the vicinity of the wheel suspension mount of a motor vehicle when itis driven fast over rough roadway surfaces or when tires are used whichhave a rough tread profile. In cases of poor insulation, the vibrationscan become noticeable in the motor vehicle as droning vibrations.

To attain an excellent uncoupling of chassis vibrations of theabove-mentioned type from a motor-vehicle, it has proven to beadvantageous when the membrane consists of a particularly flexible,rubber elastic material, for example of a material with a Shore hardnessA of 30 to 45. The shaping resistance with respect to the workingchambers that is required to attain a good damping effectiveness canstill be achieved when the lateral sides of the U-shaped profile, whichfollow one another in the radial direction and extend essentiallyparallel to the axis, have a radial thickness which conforms for themost part with their radial clearance. The corresponding axial depth ofthe recess surrounded by the U-shaped profile should correspond more orless to 2 to 4 times the value of the radial width to prevent a radialcompression and the formation of folds and, to guarantee a lowresistance to deformation in view of the spring deflection of thejournal.

A further improvement is able to be attained when the lateral side,lying radially to the inside, of the U-shaped profile of the membrane isdirectly adjacent to the journals, and the lateral side, lying radiallyto the outside, of the U-shaped profile is directly adjacent to thesupporting bearing. By this means, the U-shaped profile of the membraneexperiences reinforcement in the radial direction, which preventsinstances of eccentricity, and in view of long-term use of thesingle-thrust bearing, this guarantees a particularly uniform rollingprocess for the U-shaped profile of the membrane.

In the vicinity, of the membrane rim which projects radially to theoutside, the membrane can be axially embraced by supporting plates ofthe supporting beating which extend at essentially right angles to thedamping direction. In such a variant, the membrane can be producedindependently of the supporting plates and the supporting bearing, whichis advantageous from the standpoint of production engineering.

One is able to obtain an excellent uncoupling of acoustically disturbingvibrations by configuring the supporting plates to embrace the outwardlyprotruding rim of the membrane with axial clearance. The clearance isdimensioned so that acoustically disturbing vibrations can be absorbed,while at the same time avoiding an elastic deformation of the membranedue to simple back-and-forth movement. This type of variant completelyrules out the transfer of forces across the membrane when suchvibrations are introduced.

The above-mentioned effect manifests itself very, clearly when thesupporting plates in the vicinity of the outwardly protruding rim of themembrane are perforated like a grid in the direction of the workingchambers. The liquid volume contained between the rim and the membranecan escape more easily in the case of such a variant, thus improving therelative mobility of the membrane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a single-thrust bearing for a shock absorber, showing oneside of a longitudinal cross section, which shock absorber canconstitute part of a spring compression leg; and

FIG. 2 depicts an alternative embodiment of a single-thrust bearing fora shock absorber, showing the other side of a longitudinal crosssection, which shock absorber can constitute part of a springcompression leg.

DETAILED DESCRIPTION

In the figure, the shock absorber 1 is provided with a columnar journal2 projecting in the damping direction. The columnar journal 2 issurrounded and sealed against by an annular-shaped membrane 8. In thevicinity of the membrane rim which projects radially to the outside, themembrane is axially surrounded by two supporting plates 10, which arefixed in the supporting bearing 3. The membrane 8 and the supportingplates 10 separate two liquid-filled working chambers 4 from each other,which are interconnected by a duct-type connecting port 5. The twoworking chambers 4 are sealed off to the outside in the axial directionby flexible terminating walls 6, 7, which have a hollow-conical shape.The terminating walls 6, 7 are designed as bearing springs and are fixedat their base to the supporting bearing 3. The tips of the bearingsprings 6, 7 are turned away from each other and surround the journal 2,and have mutually opposing ends braced against one another by means ofthe journal 2. The journal 2 constitutes a part of the shock absorberwhich is not shown.

The membrane 8 has a dynamically balanced design. An alternativeembodiment of membrane 8 is depicted in FIG. 2 as membrane 16.

The variant of the membrane shown both FIG. 1 and FIG. 2 is embracedwith axial clearance by supporting plates 10 in the vicinity of its rimwhich protrudes outwardly in the radial direction. In the vicinity ofthe rim, the supporting plates 10 have a grid-type design and areprovided with perforations 11 which open in the direction of the workingchambers 4. By this means, when acoustically disturbing, high-frequencyvibrations are introduced, the rim and thus the members 8, 16 are easilydisplaceable in the damping direction relative to the supporting plate10. This substantially rules out a transfer of such vibrations to thesupporting bearing 3.

Both variants of the membranes 8, 16 are defined radially to the insideby bulge-like circumferential thickenings 9, which contact and seal aprotective sleeve 12 with elastic pre-loading. The protective sleeve 12surrounds the journal 2. The bulge-like thickenings 9 are displaceablein the damping direction relative to the protective sleeve 12 and thusto the journal 2. This substantially rules out any damage to themembrane 8, 16 when extreme inward or outward spring deflections occur.

The variant of a usable membrane shown in the FIG. 1 consists of anannular segment which projects outwardly in the radial direction andwhich is directly contiguous to the bulge-type thickening 9 which limitsthe membrane to the inside.

The membrane depicted in the FIG. 2, on the other hand, has a U-shapedprofile which protrudes in the damping direction between the thickeningand the rim which projects outwardly in the radial direction. Thisprofile embraces the journal 2 coaxially. In this case, the lateralsides of the U-shaped profile, which are located such that one side iscloser to the journal than the other and which extend essentiallyparallel to the axis, have a radial thickness which conforms for themost part with their radial clearance. In this manner and as a result ofthe small radial clearance from the protective sleeve exhibited by theinwardly-lying lateral side of the U-shaped profile, on the one hand,and the small radial clearance from the central recess of the supportingplate 10 exhibited by the radially, outwardly-lying lateral side of theU-shaped profile, on the other had, a uniform rolling process for themembrane results when vibrations are introduced which have to beabsorbed depending on operational conditions. As a result, longevity isdecisively improved.

To prevent any destruction of the single-thrust bearing in cases ofextreme inward and outward spring deflections, limit stops 13 areinstalled between the journal 2 and the supporting bearing 3. They canbe provided inside or outside of the working chambers 4.

The working chambers 4 and the connecting port 5 are completely filledwith a hydraulic fluid, for example with a mixture of glycol and water.The connecting port 5 has a duct-type design and is dimensioned so thata resonant movement of the contained bulk liquid results when vibrationsof a particularly disturbing frequency are introduced. By this means, anexcellent damping of such vibrations is effected.

On the other hand, when acoustically disturbing vibrations of a highfrequency are introduced, only an axial back-and-forth movement of theoutwardly protruding rim of the membrane 8 results inside the free spacewhich is predetermined by the axial clearance to the supporting plates.Therefore, the vibrations cannot be transmitted from the shock absorber1 to the supporting bearing 3.

In its bottom-side area, the supporting bearing 3 is provided with anangle ring 14 made of rubber elastic material which covers the upper endof a metallic spiral spring 15 in the radial direction and in the axialdirection. The hardness of the rubber elastic material used tomanufacture the angle ring 14 is selected so that droning vibrationscannot be transferred over the spiral spring and, in addition, so that acertain damping action results relative to such vibrations.

What is claimed is:
 1. A single-thrust bearing for a shock absorber,comprising:a) a columnar journal projecting in the damping direction ofthe shock absorber; b) a supporting bearing; c) a flexibleannular-shaped intermediary membrane sealing and surrounding saidcolumnar journal and having a rim area projecting radially outward, saidflexible annular-shaped intermediary membrane being secured in its rimarea to said supporting bearing; d) two liquid-filled working chambersseparated by said supporting bearing; e) a duct-type connecting port insaid supporting bearing and located radially outside of said rim area ofsaid annular-shaped intermediary membrane to allow fluid communicationbetween said two liquid-filled working chambers; f) flexible terminatingwalls sealing said two liquid-filled working chambers to the outside,and being secured and sealed on a first side to said columnar journaland on a second side to said supporting bearing; and g) hollow conesforming said flexible terminating walls and having hollow-cone tipssecured to said columnar journal, pointing away from each other andbraced against one another by means of said columnar journal.
 2. Thesingle-thrust bearing according to claim 1, wherein said flexibleannular-shaped intermediary membrane further comprises an innercircumference which is flexibly expanded by said columnar journal. 3.The single-thrust bearing according to claim 2, wherein said flexibleannular-shaped intermediary membrane further comprises a bulge-likecircumferential thickening in said inner circumference.
 4. Thesingle-thrust bearing according to claim 3, wherein said flexibleannular-shaped intermediary membrane further comprises a U-shapedprofile positioned between said bulge-like circumferential thickeningand said rim area and located radially inside said supporting bearing.5. The single-thrust bearing according to claim 3, wherein saidsupporting bearing further comprises supporting plates extending atessentially right angles to the damping direction and axially embracingsaid flexible annular-shaped intermediary membrane in the vicinity ofits rim.
 6. The single-thrust bearing according to claim 2, wherein saidflexible annular-shaped intermediary membrane further comprises aU-shaped profile positioned between said rim area and said columnarjournal and located radially inside said supporting bearing.
 7. Thesingle-thrust bearing according to claim 2, wherein said supportingbearing further comprises supporting plates extending at essentiallyright angles to the damping direction and axially embracing saidflexible annular-shaped intermediary membrane in the vicinity of itsrim.
 8. The single-thrust bearing according to claim 1, wherein saidflexible annular-shaped intermediary membrane further comprises aU-shaped profile positioned between said rim area and said columnarjournal and located radially inside said supporting bearing.
 9. Thesingle-thrust bearing according to claim 8, wherein said U-shapedprofile has a first lateral side and a second lateral side extendingessentially parallel to an axis of said columnar journal, said first andsecond lateral sides having a thickness conforming with their radialclearance from each other.
 10. The single-thrust bearing according toclaim 8, wherein said supporting bearing further comprises supportingplates extending at essentially right angles to the damping directionand axially embracing said flexible annular-shaped intermediary membranein the vicinity of its rim.
 11. The single-thrust bearing according toclaim 1, wherein said supporting bearing further comprises supportingplates extending at essentially right angles to the damping directionand axially embracing said flexible annular-shaped intermediary membranein the vicinity of its rim.
 12. The single-thrust bearing according toclaim 11, wherein said supporting plates embrace said rim with axialclearance.
 13. The single-thrust bearing according to claim 12, whereinsaid supporting plates are perforated in the vicinity of said rim like agrid in the direction of said two liquid-filled working chambers. 14.The single-thrust bearing according to claim 1, wherein said columnarjournal has a length and said flexible annular-shaped intermediarymembrane surrounds said columnar journal over only a portion of itslength.